RESUMO
The cbb(I) and cbb(II) operons encode structural genes which are important for carbon dioxide fixation via the Calvin-Benson-Bassham reductive pentose phosphate pathway in Rhodobacter capsulatus. Each operon is regulated by cognate LysR-type transcriptional activators, CbbR(I) and CbbR(II), with the product of the cbbR(I) gene, CbbR(I), able to control its own transcription under some growth conditions. Furthermore, CbbR(I) may at least partially regulate the cbb(II) operon, with significant, yet regulated transcription of the cbb(II) operon occurring in the absence of any CbbR. These results suggested the importance of additional regulators. Thus, in addition to the rather specific control exerted by CbbR, a more globally significant regulatory system, the RegA-RegB (PrrA-PrrB) two-component system, was found to contribute to transcriptional regulation of each cbb operon. The regA and regB mutant strains were found to contain constitutive levels of form I and form II RubisCO, the major proteins encoded by the cbb(I) and cbb(II) operons, respectively. In addition, DNaseI footprint analyses indicated that RegA*, a constitutively active mutant form of RegA, binds specifically to cbb(I) and cbb(II) promoter-operator regions. CbbR(I), CbbR(II), and RegA binding loci were localized relative to transcription start sites, leading to a coherent picture of how each of these regulators interacts with specific promoter-operator sequences of the cbb operons.
Assuntos
Proteínas de Bactérias/metabolismo , DNA Bacteriano/metabolismo , Regulação Bacteriana da Expressão Gênica/genética , Regulon/genética , Rhodobacter capsulatus/genética , Transativadores , Fatores de Transcrição/metabolismo , Proteínas de Bactérias/genética , Sequência de Bases , Pegada de DNA , DNA Bacteriano/genética , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Desoxirribonuclease I , Histidina Quinase , Modelos Genéticos , Dados de Sequência Molecular , Mutação , Regiões Operadoras Genéticas/genética , Regiões Promotoras Genéticas/genética , Ligação Proteica , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Rhodobacter capsulatus/enzimologia , Rhodobacter capsulatus/crescimento & desenvolvimento , Ribulose-Bifosfato Carboxilase/genética , Ribulose-Bifosfato Carboxilase/metabolismo , Alinhamento de Sequência , Fatores de Transcrição/genética , Transcrição Gênica/genéticaRESUMO
The genes encoding enzymes of the Calvin-Benson-Bassham (CBB) reductive pentose phosphate pathway in Rhodobacter capsulatus are organized in at least two operons, each preceded by a separate cbbR gene, encoding potential LysR-type transcriptional activators. As a prelude to studies of cbb gene regulation in R. capsulatus, the nucleotide sequence of a 4,537-bp region, which included cbbRII, was determined. This region contained the following open reading frames: a partial pgm gene (encoding phosphoglucomutase) and a complete qor gene (encoding NADPH:quinone oxidoreductase), followed by cbbRII, cbbF (encoding fructose 1,6-bisphosphatase), cbbP (encoding phosphoribulokinase), and part of cbbT (encoding transketolase). Physiological control of the CBB pathway and regulation of the R. capsulatus cbb genes were studied by using a combination of mutant strains and promoter fusion constructs. Characterization of mutant strains revealed that either form I or form II ribulose 1, 5-bisphosphate carboxylase/oxygenase (RubisCO), encoded by the cbbLS and cbbM genes, respectively, could support photoheterotrophic and autotrophic growth. A strain with disruptions in both cbbL and cbbM could not grow autotrophically and grew photoheterotrophically only when dimethyl sulfoxide was added to the culture medium. Disruption of cbbP resulted in a strain that did not synthesize form II RubisCO and had a phenotype similar to that observed in the RubisCO-minus strain, suggesting that there is only one cbbP gene in R. capsulatus and that this gene is cotranscribed with cbbM. Analysis of RubisCO activity and synthesis in strains with disruptions in either cbbRI or cbbRII, and beta-galactosidase determinations from wild-type and mutant strains containing cbbIp- and cbbIIp-lacZ fusion constructs, indicated that the cbbI and cbbII operons of R. capsulatus are within separate CbbR regulons.
Assuntos
Proteínas de Bactérias , Proteínas de Ligação a DNA/genética , Regulação Bacteriana da Expressão Gênica , Óperon , Via de Pentose Fosfato/genética , Rhodobacter capsulatus/genética , Fatores de Transcrição/genética , Sequência de Aminoácidos , Teste de Complementação Genética , Humanos , Dados de Sequência Molecular , Fenótipo , Regiões Promotoras Genéticas , Ribulose-Bifosfato Carboxilase/genética , Homologia de Sequência de AminoácidosRESUMO
The 3 Clostridium sordellii strains were isolated from the immunocompromised patient's infected-stool. These isolates were studied in detail. One strain revealed the weakly positive cytotoxin with human diploid fibroblasts whereas the other strain showed induration and edema (VP factor). All strains were confirmed to be Cl.sordellii with specific Cl.sordellii antitoxin. None of them harboured enterotoxin but they were very sensitive to imipenem cefoxitin, moderately sensitive to moxalactam. The role of probable pathophysiologic infection in the human bowel of these isolates are also discussed in this article.
Assuntos
Infecções por Clostridium/microbiologia , Clostridium/isolamento & purificação , Diarreia/microbiologia , Fezes/microbiologia , Adulto , Antibacterianos/farmacologia , Clostridium/efeitos dos fármacos , Feminino , Humanos , Tolerância Imunológica , Masculino , Testes de Sensibilidade MicrobianaRESUMO
Agar dilution technique susceptibility test of isolated Bacteroides fragilis from the normal healthy women's and infected gynecological patients' cervical areas were studied with current antimicrobial agents. Among the N H W group, imipenem had the lowest MIC90 while cefoxitin had the highest value. Metronidazole, chloramphenicol, imipenem and piperacillin had differentiated-lower values of MIC90 and MIC90 than the others. In the I G P group, imipenem also had the lowest value of MIC90 while benzylpenicillin had the highest value. The different values of MIC90 and MIC50 less than "1" were seen in metronidazole, chloramphenicol and imipenem. The significant role of MIC90 and MIC50 was discussed in this article. Although the isolated strains had beta-lactamase enzymes, the antimicrobials resistances were not correlated with the specific enzymes. Also in this article, the significant role of anaerobic component in mixed infection was also discussed.
